Calcaneal prosthesis

ABSTRACT

A calcaneal prosthesis system includes a body having a dorsal surface, a plantar surface, an anterior surface, and a posterior end. The posterior end has a tuberosity. The anterior surface has at least a concavity or convexity shaped for receiving a cuboid bone or mid-foot bone. The dorsal surface includes a convex or concave surface for engaging a talus bone or distal tibia. An integrally formed intramedullary (IM) nail extends from the dorsal surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.17/302,103, filed Apr. 23, 2021, which a division of U.S. patentapplication Ser. No. 16/495,925, filed Sep. 20, 2019 (U.S. Pat. No.11,096,793), which is a National Stage Application filed under 35 U.S.C.§ 371 of International Patent Application No. PCT/US2017/037209, filedJun. 13, 2017, the entireties of which are incorporated by referenceherein.

FIELD

This disclosure relates generally to medical devices and morespecifically to a calcaneal prosthesis.

BACKGROUND

Arthrodesis refers to surgical fixation of a joint, ultimately resultingin bone fusion. An arthrodesis procedure induces ankylosis performed torelieve pain or provide support in a diseased or injured joint.Tibiotalocalcaneal or tibiocalcaneal arthrodesis (“TC”) is a salvageprocedure for the treatment of joint disease or pain and dysfunction dueto arthritic ankle and subtalar joints, e.g., Charcot disease. Inperforming ankle and subtalar arthrodesis, the surgeon may wish toachieve anatomic alignment, pain relief, and a stable, plantigrade foot.Secure fixation while preserving the surrounding soft tissue can alsocontribute to a successful outcome.

Intramedullary (IM) nails (also referred to as “rods”) have been usedfor tibiotalocalcaneal or tibiocalcaneal arthrodesis. The IM nail fixesthe calcaneus, talus and tibia in alignment, for fusing these threebones together. The surgeon can lock the IM nail using bone screwsconnected to each end of the IM nail. The bone screws fix the positionof the IM nail relative to the cortical bone.

SUMMARY

In some embodiments, a calcaneal prosthesis system comprises a bodyhaving a dorsal surface, a plantar surface, an anterior surface, and aposterior end. The posterior end has a tuberosity. The anterior surfacehas at least a concavity or convexity or flat surface shaped forreceiving a cuboid bone. The dorsal surface includes a convex, concave,or flat surface for engaging a talus bone. The body has a firstpreviously formed surface defining a hole extending therethrough forreceiving an intramedullary (IM) nail. The hole extends from the plantarsurface of the body to the dorsal surface.

In some embodiments, a calcaneal prosthesis comprises a single-piecebody having a dorsal surface, an anterior surface, and a posterior end.The posterior end has a tuberosity. The anterior surface has a concavityshaped for receiving a cuboid bone or mid-foot bone(s). The dorsalsurface includes a convex surface for engaging a talus bone or distaltibia. The unitary body has an integral intramedullary (IM) nailprotruding from the dorsal surface.

In some embodiments, a method of making a calcaneal prosthesis includes:collecting image data defining a first three-dimensional (3D) model of afirst calcaneus of a patient; forming a second 3D model of a secondcalcaneus by computing a mirror image of the first 3D model about asagittal plane; adding to the second 3D model at least one surfacedefining a hole that extends through the second calcaneus, the holesized and shaped to receive an intramedullary nail; and fabricating thecalcaneal prosthesis according to the second 3D model, using an additivemanufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a medial view of a left foot with a calcaneal prosthesissystem.

FIG. 2 is a medial isometric view of the calcaneal prosthesis system ofFIG. 1 .

FIG. 3 is a posterior view of the calcaneal prosthesis system of FIG. 1.

FIG. 4 is a lateral view of the calcaneal prosthesis system of FIG. 1 .

FIG. 5 is an anterior view of the calcaneal prosthesis system of FIG. 1.

FIG. 6 is a superior view of the calcaneal prosthesis system of FIG. 1 .

FIG. 7 is a medial view of a left foot with a variation of the calcanealprosthesis system of FIG. 1 .

FIG. 7A is an enlarged detail of FIG. 7 .

FIG. 8 is a medial isometric view of a single-piece calcaneal prosthesissystem.

FIG. 9 is a posterior view of the calcaneal prosthesis system of FIG. 8.

FIG. 10 is a lateral view of the calcaneal prosthesis system of FIG. 8 .

FIG. 11 is an anterior view of the calcaneal prosthesis system of FIG. 8.

FIG. 12 is a superior view of the calcaneal prosthesis system of FIG. 8.

FIG. 13 is a posterior view of a variation of the calcaneal prosthesissystem shown in FIG. 3 .

FIG. 14 is a superior view of a variation of the calcaneal prosthesissystem of FIG. 1 .

FIG. 15 is a superior view of a variation of the calcaneal prosthesissystem of FIG. 14 .

FIG. 16 is a superior view of a variation of the calcaneal prosthesissystem of FIG. 1 .

FIG. 17 is a flow chart of a method of making the prosthesis of FIG. 1 .

DETAILED DESCRIPTION

This description of the exemplary embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. In the description, relativeterms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,”“below,” “up,” “down,” “top” and “bottom” as well as derivative thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should beconstrued to refer to the orientation as then described or as shown inthe drawing under discussion. These relative terms are for convenienceof description and do not require that the apparatus be constructed oroperated in a particular orientation. Terms concerning attachments,coupling and the like, such as “connected” and “interconnected,” referto a relationship wherein structures are secured or attached to oneanother either directly or indirectly through intervening structures, aswell as both movable or rigid attachments or relationships, unlessexpressly described otherwise.

This disclosure describes a calcaneal prosthesis having one or morepre-drilled holes configured for receiving at least an intramedullary(IM) nail. This disclosure also describes a single-piece calcanealprosthesis having an integrally formed IM nail extending from a dorsalsurface of the calcaneal prosthesis. In cases where the patient'scalcaneus has degraded, the calcaneal prosthesis provides a strong basefor retaining the IM nail in position for fusing the calcanealprosthesis, talus and tibia. Further, calcaneal prosthesis systems areprovided.

FIGS. 1-6 show a first embodiment of a calcaneal prosthesis 100. FIG. 1is a schematic diagram of a left foot having a calcaneal prosthesis 100and intramedullary nail 150 implanted therein. The calcaneal prosthesis100 is configured to approximate the shape and function of a naturalcalcaneus, including the calcaneal tuberosity 119. In some embodiments,the prosthesis 100 has a dorsal surface adapted to abut a resected talus200 or resected tibia. In some embodiments, the prosthesis 100 has ananterior surface adapted to abut a resected cuboid 202 and/or mid-footbones. In the configuration shown in FIG. 1 , the IM nail 150 isinserted through the calcaneal prosthesis 100, the talus 200 and thetibia 204, for fusing the calcaneal prosthesis 100, the talus 200 andthe tibia 204 together. In other embodiments, for a patient having aseverely degraded talus, the prosthesis 100 can have an extendedplantar-dorsal height, and the IM nail 150 is extended through thecalcaneal prosthesis 100, and directly into the tibia 204.

In some embodiments, a calcaneal prosthesis system 180 may be employedincluding the calcaneal prosthesis 100. In more detail, as shown inFIGS. 2-6 , the calcaneal prosthesis system 180 comprises a body 110having a dorsal surface 112, a plantar surface 114, a medial surface113, a lateral surface 115, an anterior surface 116, and a posterior end118. The anterior (A), medial (M) and dorsal (D) directions are shown inFIG. 2 . The posterior end 118 has a tuberosity 119. The tuberosity 119extends in an oblique direction relative to an anterior-posterior (A)direction of the body.

In some embodiments, the anterior surface 116 has a concavity, convexityor flat surface shaped for receiving the cuboid bone 202 or mid-footbone(s). For example, the anterior surface 116 can include a concavity116 c as shown in FIG. 2 . The concavity is shaped as an articulatingsurface for articulating motion with respect to the cuboid 202—ormid-foot bone(s) in a case where the surgeon makes a biplanar wedge cutto the mid-foot. In other embodiments described below with reference toFIGS. 14 and 15 , the anterior surface can include a trapezoid-shapedprojection or a trapezoid-shaped recess, respectively, for abutting aresected cuboid (not shown) and/or mid-foot bone(s), not shown.

In the example of FIGS. 2-6 , the dorsal surface 112 includes a convexsurface for engaging a talus bone 200 and/or tibia. For example, becausethe exemplary prosthesis 100 is intended for use in a fusion surgery,the dorsal surface 112 can include a trapezoid-shaped convexity 130 asshown in FIG. 2 , adapted to be received by a recess in a resected talus(not shown). The exemplary trapezoid-shaped convexity 130 has thegeneral form of a truncated pyramid, with trapezoidal surfaces on themedial, lateral, anterior and posterior sides, to facilitate an approachfrom any direction the surgeon may choose. In other embodimentsdescribed below with reference to FIG. 13 , the dorsal surface caninclude a trapezoid-shaped recess, for abutting a correspondingprojection of a resected talus (not shown). In other embodiments, aconcave or flat surface can be substituted for the convex surface on thedorsal surface 112 of the body. Further, convex surfaces can be curvedor can comprise combinations of flat and/or curved surfaces that form aprotuberance; concave surfaces can be curved or can comprisecombinations of flat and/or curved surfaces that form a recess.

The body 110 has a pre-formed surface defining a hole 104 therethroughfor receiving an IM nail 150. In particular, the previously formed hole104 may be pre-drilled, or pre-made by forging, casting and/ormachining. In other embodiments, the surfaces defining the holes 104 areformed as part of an additive manufacturing (AM) process, such as 3Dprinting or direct metal laser sintering (DMLS) as discussed below. Ifan AM process is used, the prosthesis 100 is formed as a plurality ofstacked monolayers, and holes are formed by voids at selected locationswithin the monolayers. The surfaces defining pre-formed hole 104 may bepre-planned using patient specific planning. In some embodiments, thedetailed shape of the non-degraded calcaneus is determined (e.g., by CTscan), a mirror image of the shape is formed about the mid-sagittalplane, and an AM process is used to construct the prosthesis accordingto the mirror image. A patient-specific manufacturing method for formingthe prosthesis 100 is described below in the discussion of FIG. 17 .

In other embodiments, one or more “generic” calcaneus implants can beprovided with multiple sizes. For example, after removing the degradedcalcaneal tissue, the surgeon can insert one or more calcanealprosthesis trials (not shown) for purpose of finding the standard sizecalcaneal prosthesis that most closely fits the foot anatomy of thepatient. The surgeon then implants a calcaneal prosthesis having a sizecorresponding to the most closely-fitting calcaneal prosthesis trial. Ifthe trial method is used, the surgeon can fit the calcaneal prosthesiswithout scanning the healthy calcaneus of the opposite foot.

The hole 104 extends from the plantar surface 114 of the body 110 to thedorsal surface 112 of the body 110. In the case where the prosthesis ismolded or formed by additive manufacturing (e.g., 3D printing or directmetal laser sintering), the surface defining hole 104 is formed at thesame time the prosthesis is formed. In the case where the prosthesis 100is formed by machining, the surface defining hole 104 may be formed atany time point before, during or after the machining process. Formingthe surface defining hole 104 at the beginning of machining providesmore options for stabilizing the piece of material from which theprosthesis is formed during the remainder of the machining. Forming thesurface defining hole 104 during fabrication of the calcaneal prosthesis100 reduces the length of the surgery preparation and avoids thedifficulty of the surgeon drilling an aligned hole in the irregularlyshaped calcaneal prosthesis 100.

A plurality of fastener openings (e.g., screw-receiving openings)penetrate the body 110 from the medial surface 113, lateral surface 115,anterior surface 116 and/or posterior end 118. The fastener openings105, 106 extend from the external surface of the calcaneal prosthesis100 to the hole 104. In some embodiments, the IM nail 150 has a setscrew that can be advanced within the nail to compress the joint. Insome embodiments, the surgeon can implant bone screws into the calcanealprosthesis 100 and into aligned screw-receiving holes in the IM nail, tostabilize the IM nail and prevent it from loosening or moving.Prosthesis 100 can also have surfaces defining additional fixation holesfrom medial, lateral, or posterior side of the calcaneal to fusecalcaneal to cuboid and/or mid-foot bones. For example, FIGS. 2-6 show afastener opening 106 on the medial surface 113 and a fastener opening105 on the lateral surface 115. The at least one fastener opening can beoriented at an oblique angle relative to the hole. These are justexemplary locations and orientations. The fastener opening can beprovided at different locations (not shown). The fastener openings 105,106 can be oriented at a variety of different angles. Additionalfastener openings can be included, and the number of fastener openingsis not limited to two. For example, some embodiments also have surfacesdefining additional fixation holes from medial, lateral, or posteriorside of the calcaneal to fuse calcaneal to cuboid and/or mid-foot bones.

The body 110 can have one or more openings 120 for receiving k-wires forexternal fixation. The example in FIGS. 1-6 has two openings 120, butother embodiments can have any number of openings for external fixation.The openings 120 can extend part way into the body 110 or extend fromone (e.g., lateral) side to the opposite (e.g., medial) side as shown.The k-wires can be attached to an external fixation device, such as acircular fixator or the like (not shown).

The calcaneal prosthesis system 180 further comprises an intramedullary(IM) nail 150 shaped to extend through the hole 104. The IM nail 150 hasat least one aperture 151, 152 configured to receive at least onefastener (e.g., a bone screw, not shown) extending through the at leastone fastener opening 105, 106 of the body 110.

The IM nail 150 comprises a material such as titanium, a titanium alloy(e.g., Ti 6Al-4V) or stainless steel, or cobalt chrome (CoCr).

The IM nail 150 has an elongated shape. In some embodiments, the IM nailhas a first diameter D1 along its entire length, as shown in FIG. 2 . Inother embodiments (as discussed below with reference to FIG. 7 , the IMnail has a stop to prevent the IM nail from moving toward the tibia 204when pressure is applied to the foot.

The exemplary calcaneal prosthesis system 180 allows implantation of anIM nail, even in the case where the patient's calcaneus is deteriorated,such as in the case of Charcot disease. The surgeon can replace thecalcaneus with the calcaneus prosthesis 100 and then insert the IM nail150. The calcaneus prosthesis 100 provides a strong, aligned implant forsecuring the IM nail 150. The previously formed surface defining hole104 and fastener openings 105, 106 avoid any need for the surgeon todrill through the calcaneus prosthesis 100 and avoid alignment errorsdue to incorrect drilling by the surgeon.

Although FIGS. 1-6 show a calcaneal prosthesis system 180 for a leftfoot, a calcaneal prosthesis for the right foot (not shown) can sharethe same design elements arranged as a mirror image of calcanealprosthesis system 180 with respect to the mid-sagittal plane.

In some embodiments, a method for implanting the calcaneal prosthesissystem 180 of FIGS. 1-6 comprises implanting a calcaneal prosthesis 100through a medial incision, a lateral incision, an anterior incision, ora posterior incision in a foot. For example, a method of implanting thecalcaneal prosthesis system 180 can include making an incision forinserting the calcaneal prosthesis 100 from a desired side (e.g., ananterior approach). Depending on the quality of the talar bone 200 andthe configuration of the dorsal surface of the calcaneal prosthesis 100,the surgeon may resect the talus 200 to include a recess or aprotuberance. The surgeon may place pins in the talus 200 and/or cuboid202 for aligning the calcaneal prosthesis 100 during implantation.

The calcaneal prosthesis 100 is inserted into the wound site. Thecalcaneal prosthesis 100 has a pre-planned hole 104 therethrough. Thehole 104 extends from a plantar surface 114 of the calcaneal prosthesisto a dorsal surface 112 of the calcaneal prosthesis 100. The surgeondrills to extend the hole for the IM nail 150 through the talus 200 andtibia 204 from a plantar approach. Then the IM nail 150 is insertedthrough a plantar incision in the foot and through the hole 104 of thecalcaneal prosthesis 100, through the talus 200 and into the tibia 204.The surgeon inserts one or more bone screws through a fastener opening105, 106 in a medial side 113, lateral side 115, anterior side 116, orposterior side 118 of the calcaneal prosthesis 100 and into acorresponding aperture in the IM nail 150. The fasteners (e.g., bonescrews) are inserted through the calcaneal prosthesis 100 and into theapertures 151, 152, 155 of the IM nail 150 to lock the IM nail 150 inplace. For example, the surgeon may insert three screws: a transversecalcaneal screw, a posterior calcaneal screw, and subtalar screw (if thepatient's talus is intact). The surgeon also inserts one or more bonescrews through the tibia 204 and into the IM nail 150. The calcanealprosthesis system 180 can be advantageous if the surgeon wants to use ananterior, posterior, lateral or medial approach for inserting thecalcaneal prosthesis 100.

FIG. 7 shows an embodiment of a calcaneal prosthesis system 780 in whichthe IM nail 750 has a shoulder 751, and the calcaneal prosthesis 700 hasa corresponding stop 752 for limiting a depth of insertion of the IMnail 750. FIG. 7A is an enlarged detail of FIG. 7 , showing the shoulder751 of IM nail 750 abutting the stop 752 within the hole. In FIG. 7 ,the IM nail 750 has a first portion 753 (e.g., a dorsal portion) with afirst diameter D1, and a second portion 754 (e.g., plantar portion) witha second diameter D2 different from the first diameter D1. The surfacedefining the hole in the body 700 has a first part 704 sized to receivethe first portion 753 of the IM nail 750 and a second part 705 sized toreceive the second portion 754 of the IM nail 750. The stop 752 islocated at the interface between the first part 704 and the second part705. When the IM nail 750 is inserted through the calcaneal prosthesis700 and the talus 200, the shoulder 751 of the IM nail 750 abuts thestop 752 and prevents the IM nail 750 from traveling further into thetibia 204. The stop 752 can be formed by a counter bore 705 in theplantar surface of the calcaneal prosthesis 700. In some embodiments, asshown in FIG. 7 the stop 752 is located within the calcaneal prosthesis700.

Although IM nail 750 has an increase in diameter from D1 to D2 where thefirst portion 753 meets the second portion 754, this is not arequirement. In other embodiments (not shown), the IM nail has a gradualtaper from the first diameter D1 to the second diameter D2. Thecalcaneal prosthesis 700 can have a corresponding gradual taper from thefirst diameter D1 to the second diameter D2. The tapered portion (notshown) of the surface defining the hole in the calcaneal prosthesis canact as the stop.

In another embodiment (not shown), the second portion 754 of the IM nail750 extends from the plantar surface of the calcaneal prosthesis to thedorsal surface of the calcaneal prosthesis. The surface defining hole705 has the larger diameter D2 for the entire distance from the plantarsurface of the calcaneal prosthesis 700 to the dorsal surface of thecalcaneal prosthesis. The surface defining hole 706 in the talus 200 andtibia 204 has the smaller diameter D1, and the cortical bone of thetalus 200 provides the stop 752.

The method for implanting the calcaneal prosthesis 700 is similar to themethod described above for implanting the calcaneal prosthesis system180 of FIG. 1 As noted above, the IM nail 750 has a first portion 753with a first diameter D1, a second portion 754 with a second diameter D2larger than the first diameter D1, and a shoulder 751 at an interfacebetween the first portion 753 and the second portion 754. The surfacedefining hole in the calcaneal prosthesis 700 has a first part 704 sizedto receive the first portion 753 of the IM nail 750 and a second part705 sized to receive the second portion 754 of the IM nail 750. The stepof inserting the IM nail 750 into the hole 704, 705 includes advancingthe IM nail 750 until the shoulder 751 of the IM nail 750 abuts the stop752 of the opening 705.

FIGS. 8-12 show an embodiment of a single-piece calcaneal prosthesis 800for a left foot. Except where expressly indicated below, the shape ofthe prosthesis 800 can be the same as the shape of the prosthesis 100 ofFIGS. 1-6 .

FIG. 8 is a schematic diagram of a left foot having a monolithiccalcaneal prosthesis 800 having an integral intramedullary nail 850formed of a single piece of material. The calcaneal prosthesis 800 isconfigured to approximate the shape and function of a natural calcaneus,including the calcaneal tuberosity 819. In some embodiments, theprosthesis 800 has a dorsal surface adapted to abut a resected talus 200or resected tibia 204. In some embodiments, the prosthesis 800 has ananterior surface adapted to abut a resected cuboid 202 and/or mid-footbones. In the configuration shown in FIG. 8 , the IM nail 850 isconfigured to be inserted through the talus 200 and the tibia 204, forfusing the calcaneal prosthesis 800, the talus 200 and the tibia 204together. In other embodiments, for a patient having a severely degradedtalus, the prosthesis 800 can have an extended plantar-dorsal height,and the IM nail 850 is configured to extend directly into the tibia 204.

In more detail, as shown in FIGS. 9-12 , the calcaneal prosthesis system880 comprises a body 810 having a dorsal surface 812, a plantar surface814, a medial surface 813, a lateral surface 815, an anterior surface816, and a posterior end 818. The anterior (A), medial (M) and dorsal(D) directions are shown in FIG. 8 . The posterior end 818 has atuberosity 819. The tuberosity 819 extends in an oblique directionrelative to an anterior-posterior (A) direction of the body.

In some embodiments, the anterior surface 816 has a concavity, convexityor flat surface shaped for receiving the cuboid bone 202 or mid-footbone(s). For example, the anterior surface 816 can include a concavity816 c as shown in FIG. 8 . The concavity is shaped as an articulatingsurface for articulating motion with respect to the cuboid 202 (ormid-foot bone(s) in a case where the surgeon makes a biplanar wedge cutto the mid-foot). In other embodiments described below with reference toFIGS. 14 and 15 , the anterior surface can include a trapezoid-shapedprojection or a trapezoid-shaped recess, respectively, for abutting aresected cuboid (not shown) and/or mid-foot bone(s), not shown.

In the example of FIGS. 8-12 , the dorsal surface 812 includes a convexsurface for engaging a talus bone 200 and/or tibia. For example, becausethe exemplary prosthesis 800 is intended for use in a fusion surgery,the dorsal surface 812 can include a trapezoid-shaped convexity 830 asshown in FIG. 8 , adapted to be received by a recess in a resected talus(not shown). The exemplary trapezoid-shaped convexity 830 has thegeneral form of a truncated pyramid, with trapezoidal surfaces on themedial, lateral, anterior and posterior sides, to facilitate an approachfrom any direction the surgeon may choose. In other embodimentsdescribed below with reference to FIG. 13 , the dorsal surface caninclude a trapezoid-shaped recess, for abutting a correspondingprojection of a resected talus (not shown). In other embodiments, aconcave or flat surface can be substituted for the convex surface on thedorsal surface 812 of the body. Further, convex surfaces can be curvedor can comprise combinations of flat and/or curved surfaces that form aprotuberance; concave surfaces can be curved or can comprisecombinations of flat and/or curved surfaces that form a recess.

The body 810 and IM nail 850 may be pre-drilled, or pre-made by forging,casting and/or machining. In other embodiments, the body 810 and IM nail850 are formed as part of an additive manufacturing (AM) process, suchas 3D printing or direct metal laser sintering (DMLS) as discussedbelow. If an AM process is used, the prosthesis 800 is formed as aplurality of stacked monolayers, and the k-wire holes 820 are formed byvoids at selected locations within the monolayers. The pre-formed holes820 may be pre-planned using patient specific planning. For example, thecalcaneus prosthesis 800 can be a patient-specific prosthesis designedas a mirror image of a non-degraded calcaneus of the patient's oppositefoot. The location and angulation of the implant holes and IM nail holecan be designed using a three-dimensional model to ensure that thefasteners and IM nail do not extend into one or more predeterminedsections of a corresponding three-dimensional model of the patient'stissue, as determined by X-ray imagery.

In the case where the prosthesis is molded or formed by additivemanufacturing (e.g., 3D printing or direct metal laser sintering), theIM nail 850 is formed at the same time the body 810 is formed. In thecase where the prosthesis 800 is formed by machining, the IM nail 850may be formed at any time point before, during or after machining thebody 810. Forming the surface defining hole 804 at the beginning ofmachining provides more options for stabilizing the piece of materialfrom which the prosthesis is formed during the remainder of themachining. Forming the IM nail 850 during fabrication of the calcanealprosthesis 800 reduces the length of the surgery preparation and avoidsthe difficulty of the surgeon drilling an aligned hole in theirregularly shaped calcaneal prosthesis 800.

In some embodiments, the IM nail 850 has a set screw that can beadvanced within the nail to compress the joint. Prosthesis 800 can alsohave additional surfaces defining fixation holes from medial, lateral,or posterior side of the calcaneal prosthesis 800 to fuse calcanealprosthesis 800 to cuboid and/or mid-foot bones. The fastener opening canbe provided at different locations (not shown). The fastener openingscan be oriented at a variety of different angles. Additional fasteneropenings can be included, and the number of fastener openings is notlimited to two. For example, some embodiments also have additionalsurfaces defining fixation holes from medial, lateral, or posterior sideof the calcaneal to fuse calcaneal to cuboid and/or mid-foot bones.

The body 810 can have one or more openings 820 for receiving k-wires forexternal fixation. The example in FIGS. 8-12 has two openings 820, butother embodiments can have any number of openings for external fixation.The openings 820 can extend part way into the body 810 or extend fromone (e.g., lateral) side to the opposite (e.g., medial) side as shown.The k-wires can be attached to an external fixation device, such as acircular fixator or the like (not shown).

The IM nail 850 has at least one aperture 851, 852 configured to receiveat least one fastener (e.g., a bone screw, not shown).

The IM nail 850 has an elongated shape. In some embodiments, the IM nailhas a first diameter D1 along its entire length, as shown in FIG. 8 . Inother embodiments (as discussed above with reference to FIG. 7 , the IMnail has a stop to prevent the IM nail from moving toward the tibia 204when pressure is applied to the foot.

Although FIGS. 8-12 show a calcaneal prosthesis system 880 for a leftfoot, a calcaneal prosthesis for the right foot (not shown) can sharethe same design elements arranged as a mirror image of calcanealprosthesis system 880 with respect to the mid-sagittal plane.

The single-piece calcaneal prosthesis 800 comprises a unitary (i.e.,single-piece, monolithic) body 810 having a dorsal surface 812, aplantar surface 814, an anterior surface 816, and a posterior end 818.The posterior end 818 has a tuberosity 819. The anterior surface 816 canhave a concavity 816 c shaped for receiving a cuboid bone 202 ormid-foot bone(s). In other embodiments, a convex or flat surface can besubstituted for the concavity 816 c. The dorsal surface 812 can includea convex surface 830 for engaging a talus bone 200 and/or distal tibia.In other embodiments, a concave or flat surface can be substituted forthe convexity 830. The unitary body has an integral IM nail 850protruding from the dorsal surface 812. In the example of FIG. 8 , theintegral IM nail protrudes from the convex surface 830 of the dorsalsurface 812. In other embodiments, a concave or flat surface can besubstituted for the convex surface 830. The integral IM nail 850 has atleast one aperture 851, 852 at an end of the IM nail opposite from thebody 810. The surgeon can insert fasteners (e.g., bone screws) throughthe cortical bone of the tibia 204 and/or talus 200 and into theapertures 851, 852 to fix and stabilize the IM nail 850. In someembodiments, the apertures 851, 852 are configured to receive fastenersoriented at an oblique angle relative to a longitudinal axis 840 of theIM nail 850. The body can have one or more openings 820 for receivingk-wires for external fixation.

The single-piece prosthesis 800 can eliminate separate installationsteps for the IM nail 850, and eliminate fasteners (e.g., bone screws)for fixing the IM nail 850 to the calcaneal prosthesis. The hole 104 isomitted from the calcaneal prosthesis 800, because the IM nail 850 isnot a separate piece and is not inserted into a hole in the calcanealprosthesis 800. The fastener openings 105, 106 in the side surfaces ofthe calcaneal prosthesis 100 can also be omitted, because fasteners arenot used to lock the IM nail to the calcaneal prosthesis.

The single-piece construction of prosthesis 800 eliminates the separatesteps of inserting the calcaneal prosthesis 100 and then inserting theIM nail 150, as described above with reference to FIGS. 1-7 . Thesingle-piece prosthesis is implanted from a plantar approach, and thusinvolves a larger plantar incision than the calcaneal prosthesis system180. The surgeon makes an incision in the plantar surface of the foot.Any remaining calcaneal bone is removed. The surgeon drills aplantar-dorsal hole through the talus 200 and into the longitudinal axisof the tibia 204. The talus 200 is resected (via lateral or medialapproach) to receive the dorsal convexity (or fit into a dorsalconcavity) of the calcaneal prosthesis. The prosthesis 800 is insertednail-first into the wound via plantar approach, and the IM nail 850 isinserted through the talus 200 and into the tibia 204.

FIG. 13 shows a calcaneal prosthesis system 1300 including a calcanealprosthesis 1310 that is a variation of the calcaneal prosthesis 100.Calcaneal prosthesis 1310 has a dorsal surface 1312, a plantar surface1314, an anterior surface (not shown), a medial surface 1313, a lateralsurface 1315, and a posterior end 1318. The posterior end 1318 has atuberosity 1319. The anterior surface can have a concavity shaped forreceiving the cuboid bone 202 and/or mid-foot bone(s). The calcanealprosthesis 1310 can be the same as the calcaneal prosthesis 100 exceptthat the anterior surface 1316 of the calcaneal prosthesis 1310 has aconcave recess 1330 (e.g., a trapezoid-shaped recess) instead of theconvexity 130 of calcaneal prosthesis 100. The concave recess 1330 ofthe calcaneal prosthesis 1310 is configured to receive a resected talushaving a trapezoid shaped protuberance. In all other respects, thecalcaneal prosthesis 1300 can have the same configuration as thecalcaneal prosthesis 100. For brevity, descriptions of the commonfeatures of calcaneal prosthesis 1310 and calcaneal prosthesis 100 arenot repeated.

FIG. 14 shows a calcaneal prosthesis system 1400 including a calcanealprosthesis 1410 that is a variation of the calcaneal prosthesis 100.Calcaneal prosthesis 1410 has a dorsal surface 1412, a plantar surface(not shown), a medial surface 1413, a lateral surface 1415, and aposterior end 1418. The posterior end 1418 has a tuberosity (not shown).The calcaneal prosthesis 1410 differs from the calcaneal prosthesis 100in that the anterior surface 1416 of calcaneal prosthesis 1410 can havea convex protuberance for interfacing to a resected cuboid bone 202having a trapezoidal recess. The anterior surface 1416 of calcanealprosthesis 1410 can have a trapezoidal shape. The convex protuberancecan provide added stability in the event the surgeon is going to fusethe cuboid 202 to the calcaneal prosthesis 1410. In all other respects,the calcaneal prosthesis 1410 can have the same configuration as thecalcaneal prosthesis 100. For brevity, descriptions of the commonfeatures of calcaneal prosthesis 1410 and calcaneal prosthesis 100 arenot repeated.

FIG. 15 shows a calcaneal prosthesis system 1500 including a calcanealprosthesis 1510 that is a variation of the calcaneal prosthesis 100.Calcaneal prosthesis 1510 has a dorsal surface 1512, a plantar surface(not shown), a medial surface 1513, a lateral surface 1515, and aposterior end 1518. The posterior end 1518 has a tuberosity (not shown).The calcaneal prosthesis 1510 differs from the calcaneal prosthesis 100in that the anterior surface 1516 of calcaneal prosthesis 1510 can havea concave recess for interfacing to a resected cuboid bone 202 having atrapezoidal protuberance. The anterior surface 1516 of calcanealprosthesis 1510 can have a trapezoidal shape. The concave recess canprovide added stability in the event the surgeon is going to fuse thecuboid 202 to the calcaneal prosthesis 1510. In some embodiments, thecalcaneal prosthesis 1510 has surfaces defining additional holes (notshown) configured to receive fixation screws from through the calcanealprosthesis and into the cuboid or mid-foot bones. In all other respects,the calcaneal prosthesis 1510 can have the same configuration as thecalcaneal prosthesis 100. For brevity, descriptions of the commonfeatures of calcaneal prosthesis 1510 and calcaneal prosthesis 100 arenot repeated.

FIG. 16 shows a calcaneal prosthesis system 1600 including a calcanealprosthesis 1610 that is a variation of the calcaneal prosthesis 100.Calcaneal prosthesis 1610 has a dorsal surface 1612, a plantar surface(not shown), a medial surface 1613, a lateral surface 1615, an anteriorsurface 1616, and a posterior end 1618. The external shape of calcanealprosthesis 1610 can be the same as the external surface of calcanealprosthesis 100. For brevity, a description of the external shape of thecommon features is not repeated. The posterior end 1618 has a tuberosity(not shown). The calcaneal prosthesis 1610 differs from the calcanealprosthesis 100 in that the internal structure of calcaneal prosthesis1610 has a lower average density than calcaneal prosthesis 100.Calcaneal prosthesis 1610 can be substantially hollow to reduce weight,and can optionally include struts 1645, 1646 for strength and a tube1655 extending from the plantar surface (not shown) to the convexportion 1630 of dorsal surface 1612. The struts 1645 and 1646 can beinterconnected for additional strength. The tube 1655 is configured toreceive the IM nail 150. In all other respects, the calcaneal prosthesis1610 can have the same configuration as the calcaneal prosthesis 100.

In some embodiments, the calcaneal prosthesis 1610 comprises a porousmaterial throughout the prosthesis. In some embodiments, the interior ofthe calcaneal prosthesis 1610 has a porous material with a first densityand one or more struts 1645, 1646 formed of a continuous solid materialhaving a second density greater than the first density. Other than thestruts 1645, 1646, the remainder of the volume of the calcanealprosthesis 1610 comprises the porous material. The porous material canhave the same composition and a lower density than the struts 1645,1646. A DMLS method can be used to form the calcaneal prosthesis with avariable density.

In the embodiments described above with reference to FIGS. 1-16 , thebody 110 comprises a biocompatible material from the group consisting ofmetals such as titanium, stainless steel, absorbable magnesium, metalalloys; polymers such as polyethylene, ultra-high molecular weightpolyethylene (UHMWPE), polyether ether ketone (PEEK), Polyetherketone(PEK), absorbable and non-absorbable polymers and copolymers; ceramicssuch as pyrocarbon; and combinations thereof. stainless steel. Furtherthe body 110 may be coated with materials what may enhancebiocompatibility such as, for example, plasma spray, hyaluronic acid,anti-microbial natural and synthetic polymers (e.g., vitamin E).

In the embodiments described above with reference to FIGS. 1-16 , thecalcaneal prosthesis 100 can be formed by forging, casting, machining ordirect metal laser sintering (DMLS). DMLS is an additive manufacturing(AM) process by which products can be printed using a laser or e-beamjoining sequential layers of powder metal (e.g., Ti6Al4V or CoCr orStainless Steel, for example) under automated computer control. UsingDMLS, the calcaneal prosthesis 100 can be formed as a highly porousstructure. Highly porous structures also provide good bone in-growthproperties. Alternatively, the calcaneal prosthesis 100 can be formed asa continuous solid, having a rough surface or a highly porous layer atthe surface.

For example, the calcaneal prosthesis 100 can have a porous surfacelayer with a thickness in a range from 0.01 inch to 0.1 inch. In someembodiments, the porous surface layer has a thickness in a range from0.03 inch to 0.07 inch. In one example, the porous surface layer has athickness in a range from 0.04 inch to 0.06 inch. In some embodiments, afirst portion of the surface area of the calcaneal prosthesis 100 isporous, and a second portion of the surface area of the calcanealprosthesis 100 is non-porous. For example, in the embodiment of FIGS.2-6 , the calcaneal prosthesis 100 can have rough surface or porouslayer at the dorsal surface 112 of the body 110, and/or at the anteriorsurface 116 of the body 110, with a smooth surface on the remainingsides. This is a non-exclusive example, and the calcaneal prosthesis canhave other combinations of smooth surface(s), rough surface(s) andsurfaces having a porous layer.

FIG. 17 is a flow chart of a method of making a calcaneal prosthesis asshown in FIGS. 1-16 . This method assumes that the patient's feet aresymmetrical or nearly-symmetrical about the mid-sagittal plane, exceptfor the deteriorated calcaneus in one foot.

At step 1702, a set of image data are collected to define a firstthree-dimensional (3D) model of a first calcaneus (the healthy ornon-degraded calcaneus) of a patient. The images can be collected by atomography method, such as X-ray computed tomography (CT) or magneticresonance imaging (MRI). A series of two-dimensional (2D) images(slices) of the patient's healthy calcaneus are collected. The imagesalso include the talus and tibia. The 3D model is constructed from the2D images, using a Radon transform, for example.

At step 1704, a second 3D model of a second calcaneus is formed bycomputing a mirror image of the first 3D model about a sagittal plane.

At step 1706, at least one surface defining a hole is added to thesecond 3D model. The hole extends through the second calcaneus, and issized and shaped to receive an intramedullary nail. The hole ispositioned so as to lie along the longitudinal axis of the tibia.

At step 1710, fastener holes and/or guide wire holes are added to the 3Dmodel. The location and angulation of the fastener holes and/or guidewire holes are adjusted such that the fasteners, guide wire holes and IMnail do not interfere with each other and do not contact specific tissueportions such as nerves. The location and angulation of the fastenerholes, guide wire holes and IM nail hole can be designed using athree-dimensional model to ensure that the fasteners, guide wires (e.g.,k-wires) and IM nail do not extend into one or more predeterminedsections of a corresponding three-dimensional model of the patient'stissue, as determined by tomography.

At step 1710, the calcaneal prosthesis is fabricated according to thesecond 3D model, using an additive manufacturing process. For example,the calcaneus prosthesis 100 can be a patient-specific prosthesisdesigned as a mirror image of a non-degraded calcaneus of the patient'sopposite foot.

Although the subject matter has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodiments,which may be made by those skilled in the art.

1.-25. (canceled)
 26. A calcaneal prosthesis for implantation into apatient during a calcaneal replacement surgery, comprising: a unitarybody having a posterior end that forms a tuberosity and defining anopening that communicates with at least one of a lateral side and amedial side of the unitary body; an anterior surface defining aconcavity that is shaped to form a surface that is suitable forarticulating motion with respect to a mid-foot bone; a dorsal surfacedefining a convex surface suitable for engaging at least one of a talusand a tibia; and an integral intramedullary (IM) nail protruding fromthe dorsal surface of the unitary body.
 27. The calcaneal prosthesis ofclaim 26, wherein the opening that communicates with at least one of alateral side and a medial side is configured so as to receive a k-wireto facilitate fixation while preserving surrounding soft tissue.
 28. Thecalcaneal prosthesis of claim 26, wherein the opening communicatesbetween the lateral side and the medial side.
 29. The calcanealprosthesis of claim 26, wherein the unitary body defines at least twoopenings that communicate with at least one of a lateral side and amedial side and configured so as to fixate while preserving surroundingsoft tissue.
 30. The calcaneal prosthesis of claim 26, wherein thetuberosity projects in an oblique direction relative to ananterior-posterior direction of the unitary body.
 31. The calcanealprosthesis of claim 26 manufactured via an additive technique.
 32. Acalcaneal prosthesis for use during a calcaneal replacement surgerycomprising: a unitary body having a dorsal surface, an anterior surface,and a posterior end, the unitary body having (i) an integralintramedullary (IM) nail protruding from the dorsal surface and (ii)defining an opening that communicates with at least one of a lateralside and a medial side of the unitary body so as to receive a wire tofacilitate fixation while preserving surrounding soft tissue; aposterior end of the unitary body includes a tuberosity; the anteriorsurface defining a concavity that is shaped for receiving a mid-footbone; and the dorsal surface including an extended plantar-dorsal heightdefining a trapezoid-shaped convex surface suitable for engaging atleast one of a talus and a distal tibia.
 33. The calcaneal prosthesis ofclaim 32, wherein the tuberosity extends in an oblique directionrelative to an anterior-posterior direction of the unitary body.
 34. Thecalcaneal prosthesis of claim 32, wherein the opening that communicateswith at least one of a lateral side and a medial side is configured soas to facilitate fixation while preserving surrounding soft tissue. 35.The calcaneal prosthesis of claim 32, wherein the opening communicatesbetween the lateral side and the medial side.
 36. The calcanealprosthesis of claim 32, the unitary body defines at least two openingsthat communicate with at least one of a lateral side and a medial sideof the unitary body.
 37. The calcaneal prosthesis of claim 36, whereinthe convex surface is trapezoidal.
 38. The calcaneal prosthesis of claim37, wherein the unitary body defines an opening that communicates withat least one of a lateral side and a medial side of the unitary body soas to receive a soft tissue fixation device.
 39. The calcanealprosthesis of claim 38, wherein the intramedullary nail defines at leastone aperture sized and configured to receive a fastener.
 40. Thecalcaneal prosthesis of claim 37, wherein the intramedullary naildefines at least one aperture sized and configured to receive afastener.
 41. The calcaneal prosthesis of claim 32, wherein theintramedullary nail has a constant diameter.
 42. The calcanealprosthesis of claim 32, wherein the intramedullary nail includes a stop.43. A method, comprising: collecting image data defining a firstthree-dimensional model of a first calcaneus of a patient; forming asecond three-dimensional model of a second calcaneus by computing amirror image of the first three-dimensional model about a sagittalplane; and fabricating a calcaneal replacement prosthesis having aunitary body including a posterior end that forms a tuberosity anddefining an opening that communicates with at least one of a lateralside and a medial side of the unitary body, an anterior surface defininga concavity that is shaped to form a surface that is suitable forarticulating motion with respect to a mid-foot bone, a dorsal surfacedefining a convex surface suitable for engaging at least one of a talusbone, and an integral intramedullary (IM) nail protruding from thedorsal surface.
 44. The method of claim 43, wherein the calcanealprosthesis is formed using an additive manufacturing process.
 45. Themethod of claim 43, further comprising adding at least one hole to thesecond three-dimensional model, the at least one hole sized andconfigured to receive a fixation device.
 46. The method of claim 43,further comprising positioning a k-wire within the opening thatcommunicates with at least one of a lateral side and a medial side ofthe single-piece body to facilitate fixation and preservation ofsurrounding soft tissue.
 47. A calcaneal prosthesis for implantationinto a patient during a calcaneal replacement surgery, comprising: aunitary body having a posterior end that forms a tuberosity and definingan opening that communicates with at least one of a lateral side and amedial side of the unitary body; an anterior surface defining aconcavity suitable to receive articulating movement of a mid-foot bone;a dorsal surface defining a convex surface suitable for engaging atleast one of a talus and a tibia; and an integral intramedullary (IM)nail protruding from the dorsal surface.
 48. The calcaneal prosthesis ofclaim 47, wherein the opening that communicates with at least one of alateral side and a medial side is configured so as to receive a k-wireto facilitate fixation and preservation of soft tissue.
 49. Thecalcaneal prosthesis of claim 47, wherein the opening communicatesbetween the lateral side and the medial side.
 50. The calcanealprosthesis of claim 47, wherein the unitary body defines at least twoopenings that communicate with at least one of a lateral side and amedial side.